Such a method is already known. DE 37 38 394 C1 discloses a respective device for limiting the engine speed of an internal combustion engine driving a motor vehicle at the detected idle state of the motor vehicle in order to exclude any random, unnecessary, but noise-intensive “revving up” of the internal combustion engine. The idle state of the motor vehicle is detected by the tachometer of the motor vehicle by means of a speed signal. Since the speed signal of the tachometer is configured to indicate a speed of the motor vehicle, which is to be stated as a speed range of the idle state (v=0) up to a speed above the maximum speed of a motor vehicle, the detection of whether an idle state of the motor vehicle is present or not, is not always unambiguously possible. If the speed signal of a tachometer, for example, is an impulse sequence, in which the number of impulses per time unit is proportional to the speed of the motor vehicle, the detection of the idle state of the motor vehicle does not occur until after a long detection time, in which no further impulses follow the last impulse. A reading error of the speed signal taints the detection result in case of an idle state, or very low speeds of the motor vehicle, much stronger than it would within a range of high speeds.
The principal object of the invention is to provide a method that very reliably indicates the detected idle state only with an actual idle state of the motor vehicle.